All-optical switches are emerging to offer advantages of speed, compactness and low cost per bit as the all-optical switches eliminate optical-electrical-optical (OEO) conversion. The all optical switches may be used in data center applications and fixed network telecommunication applications. Photonic integrated circuits (PIC) technology can integrate optical circuit components and electrical circuit components on a compact chip. Silicon-on-insulator (SOI) offers a platform that can provide compactness and high levels of function integration due to silicon's large index contrast.
High speed photonic switches may be based on the free carrier effect in a silicon waveguide comprising a PN and/or PIN junction. The response speed of free carrier effect-based photonic switches may be in the order of nano-seconds. The free carrier effect-based switch is typically based on a Mach-Zehnder Interference (MZI) configuration. For a 1×2 or 2×2 MZI switch, a π phase shift between the propagating light in different arms of the MZI structure is required to be applied in order to switch the light from one output to the other output of the MZI switch.
The extinction ratio of MZI switches depends upon a phase difference of the lights in the two arms at the output coupler in the MZI switch. MZI switches using the free-carrier effect may suffer from phase errors, which may result from phase imbalances of the input coupler and/or output coupler, variation of the optical absorption between the two arms of the MZI switch, and thermal-optic (TO)-effect due to driving on the PN and/or PIN junction.